Lately over the past month, i have rough idling problem when my CEL pops up. When it does, my revs flucuate from around 1000-1800, somewhere around there, on top of that, i pulled a code from my obd2 scanner tool and it reads P0113 ( something with IAT circuit/sensor), P0300 random misfire, P0301 ( cylinder 1 misfire), P0304 (cylinder 4 misfire), P0505 (i think it was IAC valve, but that was replaced by the shop recently so i don't think that's an issue unless the valve is clogged). But whenever i drive it for 300 miles, the CEL goes off, then my ECM/PCM (ECU) reverts back the car feeling with no problem except a small rough idle which i think all it takes is cleaning the IACV, but later the CEL will usually go on after 300 more miles. Tonite, i drove my car out heading to the gym and i noticed my CEL came on and when i gas it in any gear then ease off the throttle, my car chuggs somewhat of a shaky feeling even the passenger can feel. BTW, my car is a Honda Civic 99 EX 2DR 5spd transmission. And then i turned off my car for about 5 min then restarted it, it does chugg but have eratic idles as described above. I have the HELMS, Haynes, chilton repair manual, there's several causes. Any help would be appreciated . I couldn't find a thread on this type of problem so i posted it here.